Surveillance and Tracking the Outcomes of Chronic Latent EBV Infection

Inclusion Criteria: 1. immunocompetent subjects who was found to have high EBV-DNA load （\>1×103 copies/ml）in peripheral blood during the physical examination 2. Willing to be followed up by telephone or face-to-face interview Exclusion Criteria: 1. Subjects with defined immunodeficiency 2. Subjects who have taken or are going to take immunosuppressive drugs. 3. Subjects Diagnosed a validated hematopathy 4. Subjects diagnosis as precancerous lesion or malignant tumor and the life expectancy is less than 1 year. 5. psychological illness which does not allow subjects to understand the study and participate following his own free will 6. Pregnant woman 7. no written informed consent